Endoscopes have attained great acceptance within the medical community, since they provide a means for performing procedures, while enabling the physician to view the internal anatomy of the patient. Over the years, numerous endoscopes have been developed and categorized according to use in specific applications, such as cystoscopy, colonoscopy, laparoscopy, upper GI endoscopy among others. Endoscopes may be inserted into the body's natural orifices or through an incision in the skin.
An endoscope typically comprises an elongated tubular shaft, rigid or flexible, having a video camera or a fiber optic lens assembly at its distal end. The shaft is connected to a handle, which sometimes includes an ocular for direct viewing. Viewing is also usually possible via an external screen. Various surgical tools may be inserted through a working channel in the endoscope for performing different surgical procedures.
One disadvantage of existing endoscopes is their limited field of view. A limited field of view may not allow a physician to analyze an area under inspection in full detail. This in turn affects the rate of detection of pathological objects that exist in the body cavity in which the endoscope operates. For example, clinical literature shows that the average adenoma miss rate is over 24%. That is, detection of cancer is missed in more than 24 of every 100 patients. Further, from a medical industry viewpoint, unless a physician is correctly identifying cancer in at least 20% of cancer patients, the average miss rate is considered higher than industry. Therefore, there is a need in the art for endoscopes that allow a broader field of view. One approach to achieving this purpose is described in U.S. Patent Application No. 2011/0263938, which describes the use of multiple cameras or viewing elements in a single endoscope and is incorporated herein by reference.
In most embodiments of multi-camera endoscopes, CCD sensors are used as imagers in the circuit board assembly of the endoscope tip. As known in the art, CCD sensors generate analog signals while CMOS sensors generate digital signals. In a CCD sensor, every pixel's charge is transferred through a limited number of output nodes, often just one, to be converted to voltage, buffered, and sent off-chip as an analog signal. In a CMOS sensor on the other hand, each pixel has its own charge-to-voltage conversion, and the sensor often also includes amplifiers, noise-correction, and digitization circuits, so that the chip outputs digital signals. With each pixel doing its own conversion, each pixel can be accessed concurrently, thereby allowing high total bandwidth and high speed. Thus, while a CCD interface is analog and requires synchronization signals and more circuitry at the end point, CMOS is only driven by power input and generates high speed digital video interface. The use of CCD sensors requires electronics for digitizing pixels and for image processing, while CMOS sensors already contain the main blocks for digitization in the chip and require only software based processing for the images. CMOS sensor technology in recent years has leapfrogged CCDs owing to better performance, and the cost of CMOS sensors has become much lower due to a more advanced production process.
Therefore, there is a need in the art to simplify the electrical interface of the circuit board assembly used in the tip of multi viewing element endoscopes, such that it can employ CMOS sensors and support a digital interface. Such endoscopes would allow for easy control of the imagers as well as the image processing technique, while also providing a broader field of view compared to conventional single imager endoscopes. There is also need for a method of assembling CMOS sensors in the tip of multiple viewing element endoscopes so as to occupy minimum space in the limited space environment of the tip section.